On-road measurement of black carbon (BC), NOx and particle number (PN) emission factors (EF) by chasing vehicles is the first such study where BC EFs of many individual diesel cars were determined in real-world conditions. Median BC EF of diesel and gasoline cars in use for <5 years, decreased by 60% and 47% from those in use for 5–10 years. Reductions for goods vehicles' NOx and PN EFs were 52% and 67%. We found an increase of BC EFs in newer goods vehicle fleet compared to 5 – 10 year old one.